Immunocytochemical studies on the origin and deposition sites of hydrolyzable tannins

Two specific antibodies, directed toward hydrolyzable tannins, i.e. polygal loylated or oxidized derivatives of 1,2,3,4,6-penta-O-galloylglucose, and t oward an acyltransferase from oak leaves that catalyzes the biosynthesis of this principal precursor, were used in immunocytochemical studies to deter mine the intracellular sites of origin and deposition of these polyphenolic plant constituents. Immunostaining of semi-thin sections from leaves and r oots of young pedunculate oak (Quercus robur, syn, Quercus pedunculata) pla nts with market enzymes and immunogold labeling of ultra-thin sections reve aled immunoreactive sites for both enzyme and hydrolyzable tannins in chlor oplasts, cell walls and intercellular spaces. The latter non-cytoplasmic (a poplast) compartments displayed characteristic aggregations of these two ep itopes, thus indicating an intimate association of the biocatalyst and its products. Identical distribution patterns ibr hydrolyzable tannins was obse rved in leaves of Rhus typhina (sumac) and Tellima grandiflora (fringe cups ) which, however, displayed no affinity toward the galloyltransferase antib ody that had been raised against enzyme from oak. Controls with spinach lea ves, known to be devoid of tannins, were inactive in all cases. The conclus ion that, besides chloroplasts, cell walls and intercellular space serve as sites for the biosynthesis and deposition of hydrolyzable tannins was conf irmed by analyzing extracts from these non-cytoplasmic compartments. (C) 20 01 Elsevier Science Ireland Ltd. All rights reserved.